I plan to purify membrane immunoglobulin from mouse myeloma cells and human chronic lymphocyte leukemia cells by affinity chromatography in order to extensively characterize the oligosaccharide units present in membrane IgM. Glycopeptides from purified membrane IgM will be isolated and studied to establish the number and location of the oligosaccharide units on the heavy chain. The oligosaccharide types (complex or high-mannose), sugar composition, and partial sugar sequences will also be determined. Glycopeptides from membrane IgM will be compared to glycopeptides from secreted immunoglobulin to determine if differences in carbohydrate structures are important for the localization of membrane immunoglobulin in the plasma membrane. Since the Cu4 domain of membrane IgM is likely to be the region of the heavy chain interacting with the cell membrane, it too will be purified and analyzed for carbohydrate content. The overall role of glycosylation for the localization of membrane IgM in the plasma membrane will be studied by specifically inhibiting glycosylation with tunicamycin. Regeneration of nonglycosylated membrane IgM synthesized in the presence of tynicamycin will be measured in myeloma cells and compared to the regeneration of the completely glycosylated control membrane IgM.